in heart,by heart,with heart,at heart分别是什么意思?举些句子说明,

in heart 情绪高涨
Our monitor is a person who is pure in heart.
我们的班长是个心地纯洁的人.
by heart 记忆,背诵
All you have to do is learn it by heart.
你只要做的就是把它背出来.
at heart 在内心里
It is best to be young at heart.
心中保持年轻是最好的.
不好意思,with heart